A device for controlling a windscreen wiper motor has become known from DE 33 14 770 C2, which discloses an IR optoelectronic apparatus and a circuit arrangement having an I/V converter, a phase-selective rectifier and a low-pass filter. Because the IR beam receivers in dependence upon the prevailing ambient light conditions each receive, in addition to the IR useful signal emitted by the beam transmitters, an infrared light fraction of the ambient light, the fraction of the ambient light is decoupled from the total signal to provide a signal which is basically capable of further processing. Decoupling of the IR ambient light fraction from the total signal is effected by a phase-selective rectifier or by capacitive decoupling. However, this does not decouple all of the influences of the ambient light which have a disturbing effect upon the useful signal.
The above-referenced co-pending patent application discloses a device for controlling a windscreen wiping system which automatically adjusts even to extremely varying measuring conditions, in particular, to the varying damping factors of different screen types. Operation of these existing systems, however, may be influenced by other disturbing influences of the ambient light which adversely affects evaluation of the IR useful signal.